{"id":"CVE-2026-90898","aliases":["EUVD-2026-77357","GHSA-gqjq-cgxr-8c7c"],"status":"published","title":"Bifrost unauthenticated remote code execution via MCP stdio client registration","description":"Bifrost registers MCP clients through its management API. A stdio client is a command plus args. Bifrost starts that program in the gateway the moment the client is added. No MCP handshake required.\n\n\n\nThe default is governance.auth_config.is_enabled=false. Auth off means every caller is a local admin. One unauthenticated POST /api/mcp/client is enough to run a program as the Bifrost process user (appuser on the official image).\n\n\n\n transports/v2.1.0 refuses an unauthenticated stdio registration with 403. transports/v2.0.0 still allows it.","severity":{"version":"3.1","score":9.8,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","level":"critical","assessor":"cna","from":"cve"},"epss":{"day":"2026-11-10","score":0.02311,"percentile":0.83531,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":true,"fix_available":false},"cwes":["CWE-284","CWE-306"],"published":"2026-09-14T10:18:53Z","modified":"2026-10-28T02:30:40Z","exploits":[{"source":"nuclei","id":"CVE-2026-90898","title":"Bifrost \u003c 2.1.0 - Unauthenticated MCP Stdio Command Execution","type":"detection template","url":"https://github.com/projectdiscovery/nuclei-templates/blob/main/http/cves/2026/CVE-2026-90898.yaml"},{"source":"pocgithub","id":"HORKimhab/CVE-2026-90898","title":"HORKimhab/CVE-2026-90898","date":"2026-09-23","url":"https://github.com/HORKimhab/CVE-2026-90898"}],"products":[{"vendor":"brokercap","product":"bifrost"},{"vendor":"maximhq","product":"bifrost"}],"references":[{"url":"https://github.com/maximhq/bifrost/pull/6757","tags":["patch","fix"]},{"url":"https://github.com/maximhq/bifrost/commit/12e170352bd25eab1ae9ba16611f1797d1fd8fdc","tags":["patch","fix"]},{"url":"https://github.com/maximhq/bifrost/releases/tag/transports/v2.1.0","tags":["release-notes","advisory"]},{"url":"https://github.com/maximhq/bifrost","tags":["product","package"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-90898","tags":["advisory"]},{"url":"https://github.com/advisories/GHSA-gqjq-cgxr-8c7c"},{"url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/90xxx/CVE-2026-90898.json","tags":["advisory"]},{"url":"git://github.com/maximhq/bifrost","tags":["package"]}],"sources":{"cve":[{"id":"CVE-2026-90898","title":"Bifrost unauthenticated remote code execution via MCP stdio client registration","description":"Bifrost registers MCP clients through its management API. A stdio client is a command plus args. Bifrost starts that program in the gateway the moment the client is added. No MCP handshake required.\n\n\n\nThe default is governance.auth_config.is_enabled=false. Auth off means every caller is a local admin. One unauthenticated POST /api/mcp/client is enough to run a program as the Bifrost process user (appuser on the official image).\n\n\n\n transports/v2.1.0 refuses an unauthenticated stdio registration with 403. transports/v2.0.0 still allows it.","status":"published","published":"2026-09-14T10:18:53.454Z","modified":"2026-09-14T11:19:46.276Z","cvss":[{"version":"3.1","score":9.8,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","level":"critical","assessor":"cna"}],"cwes":["CWE-306","CWE-284"],"updated_at":"2026-11-02T13:45:47.885058Z"}],"euvd":[{"id":"EUVD-2026-77357","description":"Bifrost registers MCP clients through its management API. A stdio client is a command plus args. Bifrost starts that program in the gateway the moment the client is added. No MCP handshake required.\n\n\n\nThe default is governance.auth_config.is_enabled=false. Auth off means every caller is a local admin. One unauthenticated POST /api/mcp/client is enough to run a program as the Bifrost process user (appuser on the official image).\n\n\n\n transports/v2.1.0 refuses an unauthenticated stdio registration with 403. transports/v2.0.0 still allows it.","status":"published","published":"2026-09-14T10:18:53Z","modified":"2026-09-14T11:19:46Z","cvss":[{"version":"3.1","score":9.8,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","level":"critical"}],"updated_at":"2026-11-02T17:28:21.556158Z"}],"ghsa":[{"id":"GHSA-gqjq-cgxr-8c7c","title":"Bifrost registers MCP clients through its management API. A stdio client is a command plus args....","description":"Bifrost registers MCP clients through its management API. A stdio client is a command plus args. Bifrost starts that program in the gateway the moment the client is added. No MCP handshake required.\n\n\n\nThe default is governance.auth_config.is_enabled=false. Auth off means every caller is a local admin. One unauthenticated POST /api/mcp/client is enough to run a program as the Bifrost process user (appuser on the official image).\n\n\n\n transports/v2.1.0 refuses an unauthenticated stdio registration with 403. transports/v2.0.0 still allows it.","status":"published","published":"2026-09-14T12:31:40Z","modified":"2026-09-14T12:31:44Z","cvss":[{"version":"3.1","score":9.8,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","level":"critical"}],"cwes":["CWE-284"],"updated_at":"2026-11-02T15:11:49.397809Z"}],"nvd":[{"id":"CVE-2026-90898","description":"Bifrost registers MCP clients through its management API. A stdio client is a command plus args. Bifrost starts that program in the gateway the moment the client is added. No MCP handshake required.\n\n\n\nThe default is governance.auth_config.is_enabled=false. Auth off means every caller is a local admin. One unauthenticated POST /api/mcp/client is enough to run a program as the Bifrost process user (appuser on the official image).\n\n\n\n transports/v2.1.0 refuses an unauthenticated stdio registration with 403. transports/v2.0.0 still allows it.","status":"published","published":"2026-09-14T11:17:08.237Z","modified":"2026-09-18T19:31:11.37Z","cvss":[{"version":"3.1","score":9.8,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","level":"critical","assessor":"secondary"}],"cwes":["CWE-284","CWE-306"],"updated_at":"2026-11-02T14:12:46.980627Z"}],"osv":[{"id":"CVE-2026-90898","title":"Bifrost unauthenticated remote code execution via MCP stdio client registration","description":"Bifrost registers MCP clients through its management API. A stdio client is a command plus args. Bifrost starts that program in the gateway the moment the client is added. No MCP handshake required.\n\n\n\nThe default is governance.auth_config.is_enabled=false. Auth off means every caller is a local admin. One unauthenticated POST /api/mcp/client is enough to run a program as the Bifrost process user (appuser on the official image).\n\n\n\n transports/v2.1.0 refuses an unauthenticated stdio registration with 403. transports/v2.0.0 still allows it.","status":"published","published":"2026-09-14T10:18:53.454Z","modified":"2026-10-28T02:30:40.341519909Z","cvss":[{"version":"3.1","score":9.8,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","level":"critical"}],"cwes":["CWE-284","CWE-306"],"updated_at":"2026-11-02T15:45:20.269367Z"}]}}